One type of conventional cherry pitting apparatus is described in U.S. Pat. No. 3,731,615, issued May 8, 1973. FIG. 1 is a simplified side-cross-sectional view of such an apparatus. Pitting apparatus 10 of FIG. 1 includes frame 12, rotatable journals 16 and 18, sprocket 32 fixedly mounted to journal 16, sprocket 34 fixedly mounted to journal 18, and conveyor 14 looped around sprockets 32 and 34. The drive mechanism comprises motor 20, rotatable pulley 22, rotatable shaft 21, pulleys 21A and 21B fixedly attached to shaft 21, pulley 26 fixedly attached to journal 18, drive belt 24 looped around element 22 and pulley 21A, and drive belt 25 looped around pulleys 21B and 26. Motor 20 causes pulley 22 to rotate (clockwise as shown in FIG. 1), thus causing belt 24 to rotate shaft 21 clockwise and causing belt 25 to rotate pulley 26 clockwise. Rotating pulley 26 causes sprocket 34 to rotate conveyor 14 clockwise.
Conveyor 14 comprises two parallel endless chain loops 28 (each engaged with one of sprockets 32 and 34) and a set of plates 36. Each plate 36 is connected between the two chain loops 28. Only one of chain loops 28 is shown in FIG. 1, and the other is in a vertical plane parallel to the plane of FIG. 1. Fruit holders 44, which define pockets for receiving cherries (C), are fixedly attached to plates 36.
Cherries C (or other articles of fruit) fall from feed unit 58 onto holders 44, as the conveyor translates plates 36 past unit 58, so that a cherry C (or other article of fruit) is loaded into each of at east some of the pockets defined by holders 44. Preferably, water is sprayed on the cherries in the pockets to cause each cherry to float so that each cherry can easily be brushed into a preferred alignment by brush 80 as conveyor 14 translates each floating cherry past brush 80 (before the cherries reach alignment plate element 86).
Element 86 (fixedly mounted to frame 12) constrains movement of the aligned cherries which translate past it, thus retaining each cherry in the preferred alignment during the pitting operation.
As the aligned cherries translate past element 86 (i.e., past a "pitting station" of the FIG. 1 apparatus), reciprocating pitting knife assembly 100 engages the translating cherries to push out the pit from within each cherry. The pitted cherries (C') then fall out of the pockets after conveyor 14 translates the pitted cherries beyond the right end of element 86.
Pitting knife assembly 100 preferably includes two rows of pitting knives: a first row including pitting knife 101 shown in FIG. 1 (and other knives identical to knife 101), and a second row including pitting knife 102 shown in FIG. 1 (and other knives identical to knife 102). Knives 101 pit the cherries in one row of pockets while knives 102 simultaneously pit the cherries in another row of pockets. A conventional implementation of knife assembly 100 will be described with reference to FIGS. 2 and 3.
The knife assembly includes two shafts 4 which are fixedly mounted between vertically oriented plates 12A of frame 12. Plates 12A are mounted generally above element 86 (in the FIG. 1 apparatus). A portion of the knife assembly of FIGS. 2 and 3 hangs from shafts 4 (in a manner to be explained below).
The knife assembly also includes rotatably mounted drive shaft 21, which is rotated about its axis by a motor (e.g., motor 20 of FIG. 1). Cam 9 and eccentric 42 are fixedly mounted to shaft 21 (at different locations along the axis of shaft 21).
Eccentric 42 is attached at bearing 136 to eccentric shaft member 114, with eccentric 42 having freedom to rotate relative to member 114. As shaft 21 rotates about its longitudinal axis, eccentric 42 (which rotates as a unit with shaft 21) exerts force on member 114 which causes member 114 to undergo reciprocating motion as follows: the center of gravity of member 114 translates back and forth along an arc of a circle in the plane of FIG. 3, but member 114 does not rotate (about its center of gravity) in the plane of FIG. 3.
Member 114 is fixedly attached to a carriage comprising upper carriage plate 7, lower carriage plate 132, tie bar 30, and a pair of tie bars 8 (only one of bars 8 is shown in FIG. 3).
The carriage hangs from a pair of rotatably mounted swing arms 2. The upper end of each arm 2 is rotatably attached to one of parallel shafts 4. A pin 19 protrudes from the lower end of each arm 2 into a tube 120. Both tubes 120 are fixedly attached to lower carriage plate 132. Thus, as the carriage rocks back and forth (in response to rotation of eccentric 42), the carriage imparts this rocking motion to pins 19 of arms 2, thus causing arms 2 to swing back and forth on fixed shafts 4. More specifically, as the carriage rocks, pins 19 translate reciprocally as a unit with tubes 120. During the reciprocal translation of pins 19 together with tubes 120, each pin 19 rotates relative to the tube 120 which surrounds it (about the common axis of the pin and the surrounding tube).
Two parallel plunger shafts 15 extend through upper carriage plate 7 and lower carriage plate 132, each with freedom to translate in the direction of its longitudinal axis relative to the plates 7 and 132. A pitting knife assembly (including a first row of pitting knives 101 and a second row of pitting knives 102) is fixedly attached to the lower ends of shafts 15. Thus (assuming for the moment that shafts 15 are held fixed relative to the carriage), as the carriage (including plates 7 and 132) rocks back and forth, shafts 15 translate reciprocally as follows: the center of gravity of each shaft 15 translates back and forth along an arc of a circle in the plane of FIG. 3, but neither shaft 15 rotates (about its center of gravity) in the plane of FIG. 3.
However, the actual motion of shafts 15 (and the knives 101 and 102 fixedly attached thereto) is more complicated, because a mechanism (including cam 9 and rocker arm unit 33) provided to reciprocate shafts longitudinally relative to the carriage as the carriage rocks back and forth. The longitudinal motion of shafts 15 is timed relative to the swinging motion thereof (by the orientation of cam 9 relative to that of eccentric 42), so that the knives 101 and 102 undergo the following motion: knives 101 and 102 move longitudinally downward (into engagement with the cherries to be pitted) while the carriage swings in the direction of motion of the cherries (which corresponds to "toward the right" in FIG. 3), knives 101 and 102 then move longitudinally upward (until they are out of engagement with the cherries) while the carriage continues to swing in the direction of motion of the cherries, knives 101 and 102 then continue to move longitudinally upward while the carriage begins to swing in opposite direction (toward the left in FIG. 3), and finally knives 101 and 102 begin to move longitudinally downward (toward a new set of cherries to be pitted) while the carriage continues to swing in the direction opposite the direction of motion of the cherries.
We next describe the manner in which cam 9 and rocker arm unit 33 cause shafts 15 to execute longitudinally reciprocating motion. One end of rocker arm unit 33 (comprising pin 112 of unit 33) is pivotally attached to stroke adjustment screw 110. Screw 110 is adjustably attached to support bar 11, and bar 11 is fixedly attached to one of frame plates 12A. With screw 110 fastened in a selected position relative to bar 11, unit 33 is free to pivot reciprocally (both clockwise and counterclockwise in the plane of FIG. 3) about pin 112 in response to the forces alternately exerted thereon by rotating cam 9 and spring-loaded shafts 15. Before operating the apparatus, screw 110 can be repositioned relative to bar 11, in order to change the position of pin 112 and unit 33 (and thus shafts 15 engaged with unit 33) relative to the frame of the apparatus during operation. Two cam followers 40 are attached to unit 33 between the fixed end of unit 33 (the end attached to pin 112) and the free end of unit 33 (the right end in FIG. 3). A cam follower 23 protrudes from each of shafts 15 into engagement with unit 33 (near unit 33's free end), so that when unit 33 pivots clockwise in FIG. 3, unit 33 pulls cam followers 23 downward (and thus unit 33 pulls shafts 15 longitudinally downward). Shafts 15 are spring-loaded by compressing two identical springs 126 between carriage plate 132 and arm member 125 (member 125 is fixedly attached to each of shafts 15). The lower end of each spring 126 is held in position by a centering plug portion 17 of plate 132.
The outer surface (cam surface) of cam 9 engages cam followers 40. When the large radius portion of cam 9 (the portion of cam 9 having greatest radial thickness relative to the central longitudinal axis of shaft 21) rotates into engagement with cam followers 40, cam 9 pushes followers 40 down, thus pivoting the arm unit 33 clockwise about pin 112, which causes arm unit 33 to pull cam followers 23 downward, which in turn translates shafts 15 longitudinally downward relative to the carriage. As shafts 15 translate longitudinally downward relative to the carriage, spring centering arm 125 moves downward (with shafts 15) relative to the carriage, thereby compressing springs 126.
Then, when continuing rotation of shaft 21 rotates the small radius portion of cam 9 (the portion of cam 9 having less radial thickness than does the large radius portion) into engagement with cam followers 40, compressed springs 126 relax (their length increases), thus pushing arm 125 upward and causing shafts 15 to translate longitudinally upward relative to the carriage. As shafts 15 translate longitudinally upward relative to the carriage, cam followers 23 pivot arm unit 33 counterclockwise about pin 112. This pivoting motion of arm unit 33 pushes cam followers 40 upward so that cam followers 40 remain in contact with cam 9.
However, the conventional knife assembly described with reference to FIGS. 2 and 3 has several limitations and disadvantages, including the following:
the knife assembly must be spring-loaded (by compressing springs 126 between arm 125 and carriage plate 132), it must remain spring-loaded in operation (which increases power consumption, increases the cycle time of the periodic motion of shafts 15, and necessitates replacement of springs 126 from time to time as they wear out);
when motor 20 is turned off (after the knife assembly has been operating in response to rotation of shaft 21 by motor 20), springs 126 rapidly relax, thus driving shafts 15 longitudinally upward suddenly (this sudden action is potentially dangerous to workers in the vicinity of the apparatus, and increases wear and tear on the motor and other components of the apparatus, which in turn shortens the lifetime of the motor and the other components);
when motor 20 is turned off, springs 126 rapidly pull driving shafts 15 longitudinally upward and hold shafts 15 (and the pitting knives attached thereto) in their fully raised position (this is inconvenient since the operator or service technician will sometimes prefer that the knives remain in a lowered position when the motor is turned off); and
the knife assembly's set up process is difficult in the sense that, not only must springs 126 be installed and compressed, but the proper relative orientation of cam 9 and eccentric 42 must be set to ensure that shafts 15 move longitudinally up and down in proper synchronization with the rocking motion of the carriage (typically two persons are needed to set up the apparatus).
It had not been known until the present invention how to design an apparatus for pitting cherries in a manner overcoming the disadvantages and limitations of the described conventional knife assembly.